The invention relates to a method of transporting away flat flexible products stored in stack form, especially printed products, in which, in its leading edge region, each individual product is bent away downward from the underside of the stack of products by means of a suction element and is then transported away by means of a gripper that grips the leading edge region, the direction of movement of the gripper in the region of the underside of the stack of products running substantially from the leading edge region to the trailing edge region of the products in the stack of products. Furthermore, the invention relates to a device for implementing such a method.
European Patent EP 0 332 828 B1 (to which U.S. Pat. No. 5,169,283 corresponds) discloses a device which is suitable for separating a stack of paper sheets from its underside. This device has a roll-like rotary feeder which is equipped with a number of rotating satellite rolls distributed around its circumference. Each satellite roll has a row of suction elements, by means of which an individual paper sheet can be attracted by suction in each case. Paper sheets attracted in this way are conveyed along the circumference of the satellite rolls in a curved state by the rotation of said satellite rolls, being held in a conveying gap between the satellite rolls and a guide belt. After somewhat more than a half revolution of a satellite roll, carried out following the attraction of a paper sheet by suction, the paper sheet is released again by the suction elements, whereupon it is transported by the guide belt cooperating with the satellite rolls in the direction of a gripper, which grips the paper sheet and conveys it onward.
This device, disclosed by the prior art, is afflicted by the disadvantage that it is not suitable for processing comparatively thick products, since firstly the curvature carried out around the satellite rolls and secondly the dimensions of the conveying gap represent restrictions with regard to the thickness of the products.
An object of the present invention is to develop a method of the type mentioned at the beginning in such a way that flat products of an extremely wide range of types can be separated with increased throughput. A further object of the invention is to provide a device for implementing such a method.
The cited object with regard to the method is achieved, according to the invention, in that each individual product, after being bent away by means of the suction element, is transferred directly from the suction element to a gripper, so that each product is continually held either by the suction element or by the gripper while it is being bent away and while it is being transported away immediately thereafter.
As distinct from the prior art, the product to be separated is therefore guided in a controlled manner without any interruption, since it is transferred directly from the suction element to the gripper. Because of this controlled guidance, it becomes possible to operate with a considerably increased throughput, since, on account of the controlled guidance, deviation of the products from the predefined movement path, for example caused by an air draft or other action of force, can be ruled out.
It is particularly preferred if the action of drawing the product out of the stack of products begins only after the bent-away product has been gripped by the gripper.
The method according to the invention can be implemented with a particularly high throughput or reduced speed if a second product is already attracted by a suction element before a first product, previously bent away, has been drawn completely out of the stack of products. An additional increase in the throughput is even possible as a result of the fact that the second product is already attracted by a suction element before the procedure of drawing out a first product previously bent away begins. It is therefore possible to carry out the separation operation, initiated by bending a product away, in a manner overlapping in time with respect to two or even three products, so that it is possible to operate with very high throughputs.
It is advantageous if the leading edge region of the product is gripped and bent away in its central section by the suction element while the product is supported from below in its lateral regions. In this way, in addition to supporting the stack of products over the greatest possible area, it is not necessary for the suction element to be loaded in any way with the weight of the stack of products, which minimizes the economic effort to be expended with regard to the suction elements and the mounting of the suction elements.
Furthermore, it is advantageous if the product is bent away from the stack of products through an angle of between 60xc2x0 and 120xc2x0 over a deflection roll before it is gripped by the gripper, since in this case the deflection roll ensures that the product is kept taut during the entire separation operation and especially during the transfer from the suction element to the gripper, and is guided exactly on its predefined movement path. This exact guidance promotes operation with high separation throughputs. In this regard, it should be noted that the direction of movement of the gripper in the region of the underside of the stack of products runs substantially from the leading edge region to the trailing edge region of the products in the stack of product or runs obliquely to this, so that after being deflected by the deflection roll, the products are to a certain extent drawn xe2x80x9crearwardxe2x80x9d out of the stack of products.
The stack of products preferably rests with some portions of its underside on at least one rotating supporting disk that has at least one release cutout, a product being bent away when the leading edge region comes to lie in the region of the release cutout. Such a rotating supporting disk allows a product to be drawn out of the stack of products with comparatively low frictional forces, since the stack of products located above the product to be drawn out is again supported over relatively large regions by the supporting disk during the withdrawal procedure, so that the weight of the stack of products on the product to be drawn out is reduced.
It is particularly preferred if the stack of products rests with some portions of its underside on two supporting disks, which preferably rotate in opposite directions and each have at least one, especially two, diagonally opposite release cutouts, a product then being bent away when the central section of the leading edge region comes to lie in the region of a release cutout in each supporting disk in each case. As a result of the provision of two supporting disks, supporting the stack of products during the withdrawal of the lowest product may be optimized. Because of the provision of two diagonally opposite release cutouts in each supporting disk, it is possible for two products to be separated per revolution of the supporting disks, which permits operation with very high separation throughputs.
In particular when separating thin or very flexible products, it is advantageous if the central section, located in the region of the release cutout or cutouts, of the leading edge region of the lowest product of a stack of products is supported by an actively or passively moved supporting finger immediately before being bent away. On account of such a supporting finger, the lowest product is prevented from sagging downward in its central section, which would make it more difficult to attract the product properly by suction.
Instead of on rotating supporting disks, the stack of products can advantageously also rest with its underside on supporting means which move in the direction from the leading edge region to the trailing edge region of the products in the stack of products and are provided with release apertures. The products are bent away when the leading edge region comes to lie in the region of the release aperture.
The stack of products preferably rests with its underside on a number of carrier rolls, which are fixed to an intrinsically closed flexible drive element and, by means of the latter, are moved from the leading edge region to the trailing edge region of the products in the stack of products, the release apertures being formed between two adjacent carrier rolls or carrier-roll groups.
The suction element assigned to a product and the gripper assigned to the same product can move on a common conveying path or on conveying paths that run parallel to each other during the transfer of the product from the suction element to the gripper. This achieves the situation where, during the transfer of products, suction element and gripper move uniformly beside each other along an at least largely common path curve, so that no relative movements between suction element and gripper, caused by different path curves, occur, which means that the suction elements and grippers moving at the same speed on mutually corresponding path curves can be arranged with their base or carrier units in a position largely fixed in relation to one another. This results in the advantage of simplified driving and synchronization of the moving suction element and gripper parts, it additionally being possible to operate with higher throughputs on account of this simplification.
It is preferable if the suction element assigned to a product and the gripper assigned to the same product move approximately centrally along the underside of the stack of products during the transfer of the product from the suction element to the gripper. This achieves the situation where no kind of mechanical equipment has to be provided laterally beside the products to be picked up and accommodated.
The transfer of a product from the suction element to the gripper may be implemented in a particularly simple way by pivoting the suction element with respect to the gripper.
It is particularly advantageous if the stack of products is acted on, at least in some portions of its underside, by an upwardly directed intermittent force. As a result of this application of force a rapid up and down movement or a vibration of the stack of products can be produced, which ultimately effects loosening of the stack of products and permits products to be drawn out of the stack of products with reduced opposing frictional forces.
The object on which the invention is based and related to the device is achieved by the provision
of a plurality of grippers that can be moved along a gripper conveying path running underneath a stack of products,
a plurality of suction elements that can be moved along at least one suction element conveying path running underneath a stack of products, at least some portions of the suction element conveying path running along or parallel to the gripper conveying path, and
a supporting device (14, 13; 50; 67), which supports some portions of the stack (8) of products on its underside and has at least one release cutout or release aperture (26; 54).
In addition to the supporting device, this device substantially needs only a device for conveying the suction elements and the grippers. Such a device can be implemented, for example, by means of two transport wheels, of which one transports the suction elements and the other transports the grippers along the respective conveying path. However, it is preferable if only a single transport wheel is provided, which conveys both the suction elements and the grippers.
The device according to the invention can preferably be provided with respectively suitable elements for implementing the preferred method variants described above. In particular, the provision of two supporting disks, an actively or passively moved supporting finger and/or a deflection roll is advantageous, as has already been explained in the context of the description of the preferred method variants.
Finally, on the side of the stack of products, the supporting disk and/or support table can be provided with friction-reducing means, especially with compressed-air outlets. In this case, it is particularly preferable for the supporting disk to be produced from porous metal on its side facing the stack of products, since in this case the emergence of compressed air over largely the entire area, and therefore particularly efficient reduction of friction is possible.
It is particularly preferred if the especially actively driven deflection roll is mounted eccentrically or is coupled to means for producing a periodic movement oriented at right angles to the underside of the stack of products. In this way, again the loosening of the stack of products already mentioned above, and the withdrawal of products with reduced friction are made possible.
The device according to the invention can preferably also be provided with a supporting device which comprises a number of carrier rolls which are fixed to an intrinsically closed flexible drive element and form a type of rolling carpet, on which the stack of products rests with its underside. Between two adjacent carrier rolls or carrier-roll groups belonging to this supporting device, there are release apertures for the products to be bent away.
Further preferred embodiments of the method according to the invention and of the device according to the invention are defined in the dependent claims.